Typical irrigation systems use a variety of sprinkling devices depending on the size of the ground surface area that needs to be irrigated. A gear-driven rotor is commonly used to project a columnated fluid stream in excess of about 35 feet, but such rotor does not effectively or consistently project a similar stream at ranges under about 35 feet. A fixed spray head is commonly used to project a spray under about 15 feet, but such spray head does not perform effectively beyond about 15 feet. As a result, there is a gap at such mid-range distances between about 15 feet and about 35 feet from the sprinkling device where spray heads and gear-driven rotors do not effectively irrigate.
Modifying a gear-driven rotor to consistently provide a columnated fluid stream at these mid-range distances has been difficult to achieve. At such mid-range distances, the gear-drive rotor and nozzle assembly usually suffer from one of several shortcomings. For instance, modified gear driven rotors that irrigate from about 15 to about 35 feet may have insufficient fluid flows to effectively operate both the gear-drive mechanism and the valve-in-head mechanism, unacceptable nozzle performance, or unpredictable throw distances when the inlet pressures varies.
One attempt to modify a gear-driven rotor to irrigate the mid-range distances uses pressure-reducing equipment to decrease the input flow rate or fluid pressure to the rotor device itself. Such low-flow rotors achieve shorter throw distances because the fluid in the rotor has a low velocity and, therefore, does not have enough energy to travel large distances. However, because rotors often use the fluid flow to operate both a gear-drive mechanism to rotate the nozzle head and a valve-in-head mechanism as a check-valve to prevent back flow, a minimum threshold fluid flow and pressure is required to reliably operate both mechanisms in the rotor at the same time. Current low-flow rotors are not designed to function with fluid pressures and flow rates sufficient to operate the gear drive and open the valve in the rotary head in a reliable and consistent manner. In addition, decreasing the flow rate to the rotor forms a fluid stream with less energy. However, such lower-energy fluid streams are more susceptible to wind effects, which results in poor distribution and uniformity.
While reducing the fluid flow to the rotor may help achieve shorter throw distances, such low flow rates also introduce variability into the performance of the nozzle. The quality of the projected stream, as a result, is often susceptible to changes in input fluid pressure, which results in unpredictable nozzle performance. Such low-flow rotors generally have a very small range of operating pressures in which they efficiently irrigate. For example, with pressure fluctuations, the low-flow rotor will result in higher or lower fluid velocities at the nozzle exit and, therefore, longer or shorter throw distances. With large pressure increases, the low-flow rotor may experience a substantial increase in the pressure drop across the nozzle exit, which may also result in a fluid stream having much smaller fluid droplets than desired. Such a stream results in misting, which generates poor distribution and uniformity, as well as a fluid stream that is susceptible to wind effects.
The narrow pressure range of current low-flow rotors limits its practical application. Many commercial irrigation systems, such as systems installed at golf courses, usually operate at very high pressures due to the need to irrigate large areas; therefore, the low-flow rotors cannot be installed in such systems without additional pressure reducing equipment. As a result, installation becomes more difficult because the irrigation system requires pressure optimization for the low-flow rotor and expensive due to additional equipment. In many cases, the fluid pressure would need to be tailored to the specific location of each low-flow rotor with a variety of different pressure reducing equipment. Moreover, even with such pressure reducing equipment, the pressure in the system may still vary, which would also result in the unpredictable performance, such as varying throw distances or misting and poor spray distribution.
Another attempt at modifying gear-driven rotors to irrigate the mid-range distances uses more typical fluid pressures, but modifies the configuration of the nozzle exit such that the stream trajectories are altered. For example, some rotor nozzle outlet configurations have been designed to distribute a fluid having an extremely wide, wedge shaped stream or a vertically elongated stream. Such nozzle configurations attempt to effectively spread the energy of the high pressure stream over a wide surface area or spread the fluid stream vertically to layer the fluid over a smaller surface area. However, such nozzle designs often result in poor scheduling coefficients and poor distribution uniformity, which inefficiently irrigates the desired surface area. The scheduling coefficient measures how much extra watering a predetermined area must receive for every section of that area to receive sufficient water. The wide distribution often irrigates unwanted areas and the vertical distribution often irrigates too heavily. Moreover, such wide or vertical streams are also more susceptible to wind, which results in a stream that is difficult to predict and control. Similar to the low-flow rotors described above, these modified nozzle outlets are still susceptible to pressure variations that cause deviations in the throw distance and droplet size.
Rotary sprinklers have also been modified to irrigate mid-range distances utilizing multiple nozzle outlets to partition the fluid into separate fluid streams. Partitioning of the fluid divides the fluid energy between several nozzle outlets for achieving a range of throw distances and distribution patterns from a single irrigation device. For instance, a nozzle may direct a majority of the fluid through a range nozzle and then bleed a portion of the fluid through a separate spreader nozzle. Often the flow path to the spreader nozzle directs the portion of the fluid flow through an inlet opening to drop the fluid pressure and velocity prior to the spreader nozzle outlet so that such nozzle can project a fan-shaped spray of relatively narrow horizontal width short distances. While the spreader nozzle projects a spray shorter distances, it is designed only to project a small portion of the fluid in a spray distribution rather than the entire high-pressure fluid in a columnated stream similar to a range nozzle. If the entire fluid stream was directed to a spreader nozzle, the high flow rates and pressure drops that would be experienced at the nozzle outlet would result in small water droplets, nozzle misting, and unpredictable sprays that would not reliably irrigate the mid-range distances.
Modifying spray heads to project a spray pattern beyond 15 feet has also been difficult. The spray head is generally limited in size by the spray head housing; therefore, the nozzle configuration, the deflector plate size, and the typical supply pressures are restricted. Therefore, the spray pattern generally has limits to the distribution and throw distances that can be reliably achieved. For instance, at existing fluid pressures, modifying the nozzle and deflector plate configuration to project a spray further distances would result in misting, small fluid droplets, and unpredictable sprays. On the other hand, increasing fluid pressures to the spray head, even if practical, would also not reliably increase spray distances. With the limitations in the size of the nozzle housing, increasing the fluid pressure to achieve a longer throw distance will generally not result in longer throws, but large pressure drops across the nozzle outlets resulting in small fluid droplets, misting of the spray, and unpredictable distributions.
Accordingly, there is a desire for a rotary nozzle that can accommodate varying input fluid pressures to achieve precipitation rates and distribution patterns of traditional long distance range nozzles, but have a predictable throw distance and uniformity between about 15 and about 35 feet from the nozzle with sufficient flow to operate both the valve-in-head mechanism and the gear-drive mechanism.